Objective To review current status of surgical treatment for angular kyphosis in spinal tuberculosis and provide reference for clinical treatment. Methods The literature on the surgical treatment for angular kyphosis of spinal tuberculosis in recent years was extensively reviewed and summarized from the aspects of surgical indications, surgical contraindications, surgical approach, selection of osteotomy, and perioperative management. Results Angular kyphosis of spine is a common complication in patients with spinal tuberculosis. If kyphosis progresses gradually, it is easy to cause neurological damage, deterioration, and delayed paralysis, which requires surgical intervention. At present, surgical approaches for angular kyphosis of the spine include anterior approach, posterior approach, and combined anterior and posterior approaches. Anterior approach can be performed for patients with severe spinal cord compression and small kyphotic Cobb angle. Posterior approach can be used for patients with large kyphotic Cobb angle but not serious neurological impairment. A combined anterior and posterior approaches is an option for spinal canal decompression and orthosis. Osteotomy for kyphotic deformity include Smith-Peterson osteotomy (SPO), pedicle subtraction osteotomy (PSO), vertebral column resection(VCR), vertebral column decancellation (VCD), posterior vertebral column resection (PVCR), deformed complex vertebral osteotomy (DCVO), and Y-shaped osteotomy. SPO and PSO are osteotomy methods with relatively low surgical difficulty and low surgical risks, and can provide 15°-30° angular kyphosis correction effect. VCR or PVCR is a representative method of osteotomy and correction. The kyphosis correction can reach 50° and is suitable for patients with severe angular kyphosis. VCD, DCVO, and Y-shaped osteotomy are emerging surgical techniques in recent years. Compared with VCR, the surgical risks are lower and the treatment effects also improve to varying degrees. Postoperative recovery is also a very important part of the perioperative period and should be taken seriously. Conclusion There is no consensus on the choice of surgical treatment for angular kyphosis in spinal tuberculosis. Osteotomy surgery are invasive, which is a problem that colleagues have always been concerned about. It is best to choose a surgical method with less trauma while ensuring the effectiveness.
Objective To investigate the effect of the sequence of intermediate instrumentation with long screws and distraction-reduction on mild to moderate thoracolumbar fractures treated by posterior open and short-segmental fixation. MethodsThe clinical data of 68 patients with mild to moderate thoracolumbar burst fractures who met the selection criteria between January 2016 and June 2019 were retrospectively analyzed. The patients were divided into group ISDRF (intermediate screws then distraction-reduction fixation, 32 cases) and group DRISF (distraction-reduction then intermediate screws fixation, 36 cases) according to the different operation methods. There was no significant difference between the two groups in age, gender, body mass index, fracture segment, cause of injury, and preoperative load-sharing classification score, thoracolumbar injury classification and severity score, vertebral canal occupational rate, back pain visual analogue scale (VAS) score, anterior height of fractured vertebra, and Cobb angle (P>0.05). The operation time, intraoperative blood loss, complications, and fracture healing time were recorded and compared between the two groups. The vertebral canal occupational rate, anterior height of fractured vertebra, kyphosis Cobb angle, and back pain VAS score before and after operation were used to evaluate the effectiveness. Results There was no significant difference in intraoperative blood loss and operation time between the two groups (P>0.05). No vascular or spinal nerve injury and deep infections or skin infections occurred in both groups. At 1 week after operation, the vertebral canal occupational rate in the two groups was significantly improved when compared with that before operation (P<0.05), no significant difference was found in the difference of vertebral canal occupational rate before and after operation and improvement between the two groups (P>0.05). The patients in both groups were followed up 18-24 months, with an average of 22.3 months. All vertebral fractures reached bone union at 6 months postoperatively. At last follow-up, there was no internal fixation failures such as broken screws, broken rods or loose screws, but there were 2 cases of mild back pain in the ISDRF group. The intra-group comparison showed that the back pain VAS score, the anterior height of fractured vertebra, and the Cobb angle of the two groups were significantly improved at each time point postoperatively (P<0.05); the VAS scores at 12 months postoperatively and last follow-up were also improved when compared with that at 1 week postoperatively (P<0.05). At last follow-up, the anterior height of fractured vertebra in the ISDRF group was significantly lost when compared with that at 1 week and 12 months postoperatively (P<0.05), the Cobb angle had a significant loss when compared with that at 1 week postoperatively (P<0.05); the anterior height of fractured vertebra and Cobb angle in DRISF group were not significantly lost when compared with that at 1 week and 12 months postoperatively (P>0.05). The comparison between groups showed that there was no significant difference in the remission rate of VAS score between the two groups at 1 week postoperatively (P>0.05), the recovery value of the anterior height of fractured vertebra in ISDRF group was significantly higher than that in DRISF group (P<0.05), the loss rate at last follow-up was also significantly higher (P<0.05); the correction rate of Cobb angle in ISDRF group was significantly higher than that in DRISF group at 1 week postoperatively (P<0.05), but there was no significant difference in the loss rate of Cobb angle between the two groups at last follow-up (P>0.05). ConclusionIn the treatment of mild to moderate thoracolumbar burst fractures with posterior short-segment fixation, the instrumentation of long screws in the injured vertebrae does not affect the reduction of the fracture fragments in the spinal canal. DRISF can better maintain the restored anterior height of the fractured vertebra and reduce the loss of kyphosis Cobb angle during the follow-up, indicating a better long-term effectiveness.
【Abstract】 Objective To evaluate the surgical management of rigid post-traumatic thoracolumbar kyphosis (RPTK) by simultaneous posterio-anterior circumferential releasing, correction and anterior corpectomy with preserved posterior vertebral wall. Methods Twenty patients with RPTK were treated between October 2004 and October 2010 by posterior releasing, anterior subtotal corpectomy with preserved posterior vertebral wall, correction, strut graft, and short segmental fixation. There were 14 males and 6 females with an average age of 43.2 years (range, 23-63 years). The time between injury and operation was 4 months to 23 years (mean, 1.4 years). The affected locations were T11 in 1 case, T12 in 8 cases, L1 in 10 cases, and L2 in 1 case. The Cobb angle and the intervertebral height of the fractured vertebra body were measured before and after operations. The degrees of low back pain were assessed by Japanese Orthopaedic Association (JOA) scores. Results No incision infection, nerve injury, or cerebral spinal fluid leakage occurred. Seventeen patients were followed up 1-5 years with an average of 2.8 years. The JOA score at last follow-up (26.2 ± 3.9) was significantly improved when compared with the pre-operative score (14.0 ± 5.7) (t=4.536, P=0.001). One patient had aggravation of kyphosis at 3 months postoperatively, who was in stabilized condition after prolonging immobilizated time. The Cobb angle was corrected from (43.2 ± 11.5)° preoperatively to (9.8 ± 5.7)° at last follow-up, showing significant difference (P lt; 0.01). There was significant difference in the intervertebral height of the fractured vertebra body between preoperation and last follow-up (P lt; 0.05). The intervertebral height of fractured vertebra was restored to 87.0% ± 11.2% of adjacent disc height. Conclusion Posterio-anterior circumferential releasing and anterior corpectomy with preserved posterior vertebral wall can achieve satifactory clinical results, not only in pain relieving, kyphosis correction, vertebral height restoration, and spinal stability restoration, but also in the risk reduce of bleeding and spinal cord disturbance.
Objective To investigate the imaging characteristics of cervical kyphosis and spinal cord compression in cervical spondylotic myelopathy (CSM) with cervical kyphosis and the influence on effectiveness. Methods The clinical data of 36 patients with single-segment CSM with cervical kyphosis who were admitted between January 2020 and December 2022 and met the selection criteria were retrospectively analyzed. The patients were divided into 3 groups according to the positional relationship between the kyphosis focal on cervical spine X-ray film and the spinal cord compression point on MRI: the same group (group A, 20 cases, both points were in the same position), the adjacent group (group B, 10 cases, both points were located adjacent to each other), and the separated group (group C, 6 cases, both points were located >1 vertebra away from each other). There was no significant difference between groups (P>0.05) in baseline data such as gender, age, body mass index, lesion segment, disease duration, and preoperative C2-7 angle, C2-7 sagittal vertical axis (C2-7 SVA), C7 slope (C7S), kyphotic Cobb angle, fusion segment height, and Japanese Orthopedic Association (JOA) score. The patients underwent single-segment anterior cervical discectomy with fusion (ACDF). The occurrence of postoperative complications was recorded; preoperatively and at last follow-up, the patients’ neurological function was evaluated using the JOA score, and the sagittal parameters (C2-7 angle, C2-7 SVA, C7S, kyphotic Cobb angle, and height of the fused segments) were measured on cervical spine X-ray films and MRI and the correction rate of the cervical kyphosis was calculated; the correlation between changes in cervical sagittal parameters before and after operation and the JOA score improvement rate was analyzed using Pearson correlation analysis. Results In 36 patients, only 1 case of dysphagia occurred in group A, and the dysphagia symptoms disappeared at 3 days after operation, and the remaining patients had no surgery-related complications during the hospitalization. All patients were followed up 12-42 months, with a mean of 20.1 months; the difference in follow-up time between the groups was not significant (P>0.05). At last follow-up, all the imaging indicators and JOA scores of patients in the 3 groups were significantly improved when compared with preoperative ones (P<0.05). The correction rate of cervical kyphosis in group A was significantly better than that in group C, and the improvement rate of JOA score was significantly better than that in groups B and C, all showing significant differences (P<0.05), and there was no significant difference between the other groups (P>0.05). The correlation analysis showed that the improvement rate of JOA score was negatively correlated with C2-7 angle and kyphotic Cobb angle at last follow-up (r=−0.424, P=0.010; r=−0.573, P<0.001), and positively correlated with the C7S and correction rate of cervical kyphosis at last follow-up (r=0.336, P=0.045; r=0.587, P<0.001), and no correlation with the remaining indicators (P>0.05). Conclusion There are three main positional relationships between the cervical kyphosis focal and the spinal cord compression point on imaging, and they have different impacts on the effectiveness and sagittal parameters after ACDF, and those with the same position cervical kyphosis focal and spinal cord compression point have the best improvement in effectiveness and sagittal parameters.
Objective To discuss the main points of technique and the range of fusion in posterior operation of spinal stenosis associated with lumbar degenerative kyphosis (LDK). Methods The cl inical data were retrospectively analysedfrom 20 cases of spinal stenosis associated with LDK which were performed posterior operation from February 2001 to February 2008. There were 1 male and 19 females, aged 52-81 years old with an average of 64 years old. The course of disease was 6-10 years. All patients had severe low back pain. According to Frankel’s neurologic function classification, there were 18 cases of grade E and 2 cases of grade D before operation. The apex of LDK included L1 in 3 cases, L2 in 10 and L3 in 7. The operational method was decided according to different characteristics of LDK. All patients were divided into three groups. Group 1 included 6 cases of sciatica and intermittent claudication with worse physical status, the segmental decompression of spinal canal, posterior intervertebral fusion and short transpedical instrument fixation were performed. Group 2 included 8 cases whose Cobb angle of LDK was less than 20°, the segmental decompression of spinal canal, posterior intervertebral fusion and one-level or multilevel lamina osteotomy were performed, instrumentation-assisted correction was used. Group 3 included 6 cases whose Cobb angle of LDK was more than 20°, the canal decompression and one-level transvertebral wedge osteotomy were performed, instrumentation-assisted correction, intervertebral fusion and posterior-lateral fusion were used. Results Incision healedby first intention in all patients. One patient suffered from superior mesenteric artery syndrome at 6 hours after operationand healed after symptomatic management. The neurologic function was improved to grade E at 2 weeks after opeartion. All patients were followed-up 24-54 months (average 26 months). At last follow-up，the Oswestry Disabil ity Index of all patients was 30.5% ± 9.6%; showing significant difference when compared with preoperation (55.9% ± 11.8%, P lt; 0.05). The back pain scoring and leg pain scoring were 2.8 ± 1.6 and 2.4 ± 1.6, respectively according to the Numeric Rating Scale score; showing significant differences when compared with preoperation (7.5 ± 0.5 and 7.3 ± 0.7, P lt; 0.05). The Numeric Rating Scale score and Oswestry Disabil ity Index in all patients were improved obviously when compared with before operation (P lt; 0.05). During the follow-up period, there was no instrumentation failure or correction loss and the fusion rate was up to 100%. Conclusion For spinal stenosis associated with LDK patients, the most important therapic purpose is to improve cl inical symptom through reconstruction lumbar stabil ization and spinal biomechanics l ine in sagittal plane. Overall estimate of the cl inical appearance and imageology character is necessary when making decision of which segments needed to be fixation and fusion. Individual ized treatment strategy may be the best choice.
Objective To investigate the effectiveness of trans-intervertebral space osteotomy (TIO) combined with cage implantation in treatment of old thoracolumbar compression fracture with kyphosis. Methods A clinical data of 59 patients with old thoracolumbar compression fracture and kyphosis, who met the selection criteria between January 2010 and August 2020, was retrospectively analyzed. Among them, 20 cases underwent TIO combined with cage implantation (group A), 21 patients underwent TIO (group B), and 18 patients underwent pedicle subtraction osteotomy (PSO; group C). There was no significant difference in gender, age, time from injury to operation, fracture segment, and preoperative Cobb angle, average height of functional spinal unit (FSU), sagittal vertical axis (SVA), visual analogue scale (VAS) score, Japanese Orthopedic Association (JOA) score, and Oswestry disability index (ODI) between groups (P>0.05). The operation time, intraoperative blood loss, and postoperative complications were recorded. Imaging review was performed to observe the fusion of the bone graft. Cobb angle, average height of FSU, and SVA were measured. VAS score, JOA score, and ODI were used to evaluate the degree of low back pain and lumbar function. Frankel grading was used to evaluate neurological function. Results The operations of 3 groups were successfully completed. The operation time and intraoperative blood loss were significantly lower in groups A and B than in group C (P<0.05); there was no significant difference between group A and group B (P>0.05). All incisions healed by first intention. Patients in all groups were followed up 23-27 months, with an average of 24.8 months. There was no significant difference in follow-up time between groups (P>0.05). At last follow-up, VAS score, JOA score, ODI, and SVA of 3 groups significantly improved when compared with those before operation (P<0.05), there was no significant difference in the differences of pre- and post-operation between groups (P>0.05). The neurological function grading of 3 groups was Frankel grade E. The Cobb angle and the average height of FSU in 3 groups at immediate and last follow-up significantly improved when compared with preoperative ones (P<0.05), there was no significant difference between immediately after operation and last follow-up (P>0.05). And there were significant differences in above indexes between groups at each time point (P<0.05). At last follow-up, the osteotomy site fused without internal fixation failure or pseudarthrosis formation were observed in 3 groups. ConclusionFor patients with old thoracolumbar compression fractures with kyphosis, the effectiveness of TIO combined with cage implantation is satisfactory. Compared with TIO and PSO, it can obtain more deformity correction degree and less invasive.
Objective To evaluate the effectiveness of using pedical screw at the fracture level, intervertebral distraction, and Cage insertion by posterior approach to treat thoracolumbar kyphosis caused by old fracture. Methods Between June 2008 and June 2010, 15 cases of thoracolumbar kyphosis caused by old fracture were treated with pedical screw at the fracture level, intervertebral distraction, and Cage insertion by posterior approach. There were 9 males and 6 females with a mean age of 54.6 years (range, 39-65 years). The disease duration was 5 months to 3 years with an average of 1.5 years. Fractured segments included T11 in 1 case, T12 in 4 cases, L1 in 5 cases, and L2 in 5 cases. Ten patients had nerve symptom, according to American Spinal Injury Association (ASIA) grading, 3 cases were classified as grade B, 4 cases as grade C, and 3 cases as grade D, of which 3 cases had sexual and sphincter dysfunction. At preoperation, the Cobb angle was (47.4 ± 10.2)°; the Oswestry disability index (ODI) score was 67.9% ± 6.9%; and the visual analogue scale (VSA) was 8.6 ± 1.4. Results The wounds obtained primary healing. The mean follow-up time was 28 months (range, 13-60 months). X-ray films showed intervertebral bone fusion was obtained within 6-11 months (mean, 10.2 months). No fixation loosening or breaking occurred during follow-up. Kyphosis was corrected, and lumbar back pain was relieved. At 1 year after operation, Cobb angle was significantly corrected to (13.3 ± 7.7)° (t=72.80, P=0.00); ODI score was significantly improved to 25.2% ± 4.6% (t=48.04, P=0.00); VAS score was significantly decreased to 2.3 ± 0.6 (t=26.52, P=0.00). According to ASIA grading in 10 patients with spinal cord injury, the spinal cord function was improved by 1 grade in 8 cases (3 cases from grade B to C, 3 cases from grade C to D, and 2 cases from grade D to E); 3 patients with sexual and sphincter dysfunction recovered in different degrees. Conclusion Using pedical screw at the fracture level, intervertebral distraction, and Cage insertion by posterior approach is an effective method to treat thoracolumbar kyphosis caused by old fracture.
Objective To investigate the effectiveness of multilevel Ponte osteotomies on maintenance and restoration of thoracic kyphosis in idiopathic scoliosis (IS) surgery. Methods Between March 2008 and February 2010, 42 patients with thoracic IS (Lenke type 1 curves) were corrected with posterior pedicle screw system. Multilevel Ponte osteostomies for posterior release was performed in 17 cases (group A), and the 3 segments near the apical vertebrae were selected as the osteotomy site; simple posterior soft tissue release was given in 25 cases (group B). There was no significant difference in sex, age, disease duration, lesion segments, coronary Cobb angle, thoracic kyphosis, Risser index, and bending flexibility between 2 groups (P gt; 0.05). The anteroposterior and lateral standing radiographs of the spine were taken to compare the effectiveness between 2 groups. Results Operation was successfully completed in all patients. The operation time and blood loss in group A were significantly greater than those in group B (P lt; 0.05). Spine dural injury and leakage of cerebrospinal fluid occurred in 1 case of group A, which was cured after compression on local area of the wound; the other patients had no intraoperative complications. The patients were followed up 2-4 years (mean, 2.8 years); no nerve injury, infection, or internal fixation failure occurred. No obvious correction loss was observed and the appearance and trunk balance were significantly improved. The coronal Cobb angles at 1 week and 2 years after operation were significantly improved when compared with preoperative ones in 2 groups (P lt; 0.05). There was no significant difference in the coronal Cobb angle and correction rate between 2 groups at 1 week and 2 years after operation (P gt; 0.05). Group A was significantly better than group B in the thoracic kyphotic angle and angle changes at 1 week and 2 years after operation (P lt; 0.05). Conclusion The posterior approach surgery with multilevel Ponte osteotomies can restore the thoracic kyphosis in IS, but it has no effect on coronal correction in Lenke type 1 curves.
ObjectiveTo explore the clinical characteristics and surgical treatment strategies of delayed spinal cord injury (SCI) caused by atypical compression of old thoracolumbar fracture.MethodsBetween January 2011 and June 2018, 32 patients with delayed SCI caused by atypical compression of old thoracolumbar fracture who met the inclusion criteria were admitted and divided into group A (20 cases, underwent anterior subtotal vertebral body resection+titanium mesh reconstruction+screw rod internal fixation) and group B (12 cases, underwent posterior 270° ring decompression of vertebral canal+titanium mesh reconstruction+screw rod internal fixation) according to the different operation approaches. There was no significant difference between the two groups in age, gender, cause of injury, fracture segment, disease duration, preoperative American Spinal Injury Association (ASIA) classification, and preoperative back pain visual analogue scale (VAS) score, lumbar Japanese Orthopaedic Association (JOA) score, kyphosis angle, and vertebral canal occupational ratio (P>0.05). The incision length, operation time, intraoperative blood loss, complications, and bone fusion time of reconstructed vertebrae were recorded and compared between the two groups; the kyphosis angle, back pain VAS score, and lumbar JOA score were used to evaluate the effectiveness.ResultsExcept that the incision length in group A was significantly shorter than that in group B (t=−4.865, P=0.000), there was no significant difference in intraoperative blood loss and operation time between the two groups (P>0.05). There was no deaths or postoperative paraplegia cases in the two groups, and no deep infection or skin infection occurred. There was 1 case of cerebrospinal fluid leakage, 1 case of inferior vena cava injury, and 1 case of chyle leakage in group A. No serious complications occurred in group B. There was no significant difference in the incidence of complications between the two groups (P=0.274). All 32 patients were followed up 12-61 months, with an average of 20.8 months. The follow-up time for groups A and B were (19.35±5.30) months and (23.25±12.20) months respectively, and the difference was not significant (t=−1.255, P=0.219). The reconstructed vertebrae in all cases obtained bony fusion postoperatively. The fusion time of groups A and B were (8.85±2.27) months and (8.50±2.50) months respectively, and the difference was not significant (t=0.406, P=0.688). The kyphosis angle, back pain VAS score, and lumbar JOA score of the two groups at each time point after operation and last follow-up were significantly improved when compared with preoperatively (P<0.05); the lumbar JOA score was further improved with time postoperatively (P<0.05), while the kyphosis angle and the VAS score of back pain remained similarly (P>0.05). Comparison of kyphosis angle, back pain VAS score, and lumbar JOA score between the two groups at various time points postoperatively showed no significant difference (P>0.05). At last follow-up, the JOA score improvement rate in groups A and B were 83.87%±0.20% and 84.50%±0.14%, respectively, and the difference was not significant (t=–0.109, P=0.914); the surgical treatment effects of the two groups were judged to be significant.ConclusionIn the later stage of treatment of old thoracolumbar fractures, even mild kyphosis and spinal canal occupying may induce delayed SCI. Surgical correction and decompression can significantly promote the recovery of damaged spinal cord function. Compared with anterior approach surgery, posterior approach surgery has the advantages of less trauma, convenient operation, and fewer complications, so it can be preferred.
Objective To investigate the feasibility of predicting proximal junctional kyphosis (PJK) in adults after spinal deformity surgery based on back-forward Bending CT localization images and related predictive indicators. Methods A retrospective analysis was performed for 31 adult patients with spinal deformity who underwent posterior osteotomy and long-segment fusion fixation between March 2017 and March 2020. There were 5 males and 26 females with an average age of 62.5 years (range, 30-77 years). The upper instrumented vertebrae (UIV) located at T5 in 1 case, T6 in 1 case, T9 in 13 cases, T10 in 12 cases, and T11 in 4 cases. The lowest instrumented vertebrae (LIV) located at L1 in 3 cases, L2 in 3 cases, L3 in 10 cases, L4 in 7 cases, L5 in 5 cases, and S1 in 3 cases. Based on the full-length lateral X-ray film of the spine in the standing position before and after operation and back-forward Bending CT localization images before operation, the sagittal sequence of the spine was obtained, and the relevant indexes were measured, including thoracic kyphosis (TK), lumbar lordosis (LL), local kyphosis Cobb angle (LKCA) [the difference between the different positions before operation (recovery value) was calculated], kyphosis flexibility, hyperextension sagittal vertical axis (hSVA), T2-L5 hyperextension C7-vertebral sagittal offset (hC7-VSO), and pre- and post-operative proximal junctional angle (PJA). At last follow-up, the patients were divided into PJK and non-PJK groups based on PJA to determine whether they had PJK. The gender, age, body mass index (BMI), number of fusion segments, number of cases with coronal plane deformity, bone mineral density (T value), UIV position, LIV position, operation time, intraoperative blood loss, osteotomy grading, and related imaging indicators were compared between the two groups. The hC7-VSO of the vertebral body with significant differences between groups was taken, and the receiver operating characteristic curve (ROC) was used to evaluate its accuracy in predicting the occurrence of PJK. Results All 31 patients were followed up 13-52 months, with an average of 30.0 months. The patient’s PJA was 1.4°-29.0° at last follow-up, with an average of 10.4°; PJK occurred in 8 cases (25.8%). There was no significant difference in gender, age, BMI, number of fusion segments, number of cases with coronal plane deformity, bone mineral density (T value), UIV position, LIV position, operation time, intraoperative blood loss, and osteotomy grading between the two groups (P>0.05). Imaging measurements showed that the LL recovery value and T8-L3 vertebral hC7-VSO in the PJK group were significantly higher than those in the non-PJK group (P>0.05). There was no significant difference in hyperextension TK, hyperextension LL, hyperextension LKCA, TK recovery value, LL recovery value, kyphosis flexibility, hSVA, and T2-T7, L4, L5 vertebral hC7-VSO (P>0.05). T8-L3 vertebral hC7-VSO was analyzed for ROC curve, and combined with the area under curve and the comprehensive evaluation of sensitivity and specificity, the best predictive index was hC7-L2, the cut-off value was 2.54 cm, the sensitivity was 100%, and the specificity was 60.9%. Conclusion Preoperative back-forward Bending CT localization image can be used to predict the occurrence of PJK after posterior osteotomy and long-segment fusion fixation in adult spinal deformity. If the patient’s T8-L2 vertebral hC7-VSO is too large, it indicates a higher risk of postoperative PJK. The best predictive index is hC7-L2, and the cut-off value is 2.54 cm.