Faculty Bibliography

BACKGROUND CONTEXT: Degenerative lumbar stenosis (DLS) patients adopt forward-bending posture as a compensatory mechanism, increasing spinal canal and foraminal volume. Previous data show laminectomy 6 short segment fusion results in improvement of sagittal vertical axis (SVA), pelvic tilt (PT) and PI-LL (pelvic incidence-lumbar lordosis) mismatch by SRS-Schwab classification in <25% of patients. The magnitude of deformity for which a DLS patient should have realignment remains unknown. PURPOSE: To identify differences in compensatory mechanisms between DLS and adult spinal deformity (ASD) patients with increasing, and to identify at what point DLS patients recruit ASD-type compensatory mechanisms. STUDY DESIGN/SETTING: Retrospective clinical and radiological review. PATIENT SAMPLE: Baseline X-ray images of 239 patients without spinal instrumentation, with the clinical radiological and diagnosis of DLS or ASD were assessed for patterns of spino-pelvic compensatory mechanisms. Patients were stratified by sagittal vertical axis (SVA) by the Schwab-SRS classification. OUTCOME MEASURES: Radiographic spino-pelvic parameters were measured in the DLS and ASD groups, including SVA, PI-LL, T1SPi, TPA and PT. METHODS: Patients were identified using a single-institution database with sole diagnosis of DLS, >40 years and if they had any of the following: PT >25degree, SVA >5cm, thoracic kyphosis (TK) >60degree or PI-LL mismatch >10degree. The patient's diagnosis was taken from the patient history chart based on correlation between history, examination and available imaging. Matched cohort with sole diagnosis of ASD was identified. Groups were stratified by SVA using Schwab-SRS classification: 0(<4cm), +(4-9.5cm), ++( >9.5cm). Sagittal spino-pelvic parameters were compared between the 2 groups with unpaired t-test. RESULTS: 239 patients were identified (122 DLS, 117 ASD). There was no difference in age or pelvic incidence between DLS and ASD with SVA stratifications. DLS patients with SVA 0 had less PT (19.8degree vs 29.2degree p<0.0001), less PI-LL mismatch (3.3degree vs 15.8degree, p<0.001), lower TPA (14.6degree vs 21.8degree, p<0.001) but higher T1SPi (-5.17degree vs -7.44degree, p< 0.001) than those with ASD. DLS patients with SVA+ had less PT (22.6degree vs 26.1degree, p=0.019) and higher T1SPi (0.64degree vs -0.70degree, p=0.008) than ASD patients. DLS patients resembled a decompensated deformity with a higher T1SPi relative to TPA when compared to the ASD cohort in groups 0 and +. No significant differences between ASD and DLS for any parameters in the SVA++ group were identified. No difference was found between DLS or ASD in TK for SVA groups 0, + or ++. CONCLUSIONS: The difference in PI-LL observed in ASD/DLS group '0' underlies the pathogenesis of ASD vs DLS. DLS patients increase SVA for neuronal decompression but without a PI-LL mismatch, they need not increase PT. As PI-LL increases in SVA >9.5cm, recruitment of PT ensues as the need for alignment overtakes desire for decompression. Their compensatory mechanism then resembles ASD. Laminectomy 6 fusion may be more appropriate for DLS patients with SVA< 9.5cm. Given <25% of patients improve in classification after fusion, surgeons should consider realignment surgery in DLS with SVA >9.5cm. Further understanding of HRQOL scores in mal-aligned DLS patients is required to best understand the importance of alignment in DLS

BACKGROUND CONTEXT: Osteoarthritis of the hip often co-exists with sagittal spinal deformity (SSD). Clinical manifestations overlap, and debate exists whether spinal deformity correction or total hip arthroplasty (THA) should be performed first. Hip extension and pelvic tilt are important compensatory mechanisms in SSD. In theory, spinal deformity correction may cause reciprocal changes in acetabular position. PURPOSE: To assess the changes in acetabular anteversion (AV) as a result of SSD correction, and to quantify the relationship between changes in AV and spino-pelvic parameters. STUDY DESIGN/SETTING: Retrospective analysis of a multicenter prospective database of adult spinal deformity patients. PATIENT SAMPLE: SSD patients who underwent surgical realignment were reviewed and included if they had a THA on baseline radiographs. Patients were excluded if they had large metal-on-metal bearings or revision THA in the study period. OUTCOME MEASURES: Radiographic anteversion of the acetabular component was measured pre- and postoperatively, and compared to the changes in spino-pelvic parameters as result of SSD correction. METHODS: Acetabular anteversion (AV) was calculated via the ellipse method (Lewinneck) on a standing PA 36" X-ray image with a wellcentered pelvis to avoid projectional measurement error. AV was measured preoperatively, and on the 6-week or 3-month postoperative X-ray study. Spino-pelvic parameters were measured including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), T1-pelvic angle (TPA), sagittal vertical axis (SVA), truncal tilt (T1SPi) and thoracic kyphosis (TK). Correlation coefficient and linear regression was performed to assess their relationships. RESULTS: Forty-one hips (33 patients) were identified. AV reduces after SSD correction by a mean 4.9degree (range +2 to -23). The change in AV was significantly correlated with the changes in PT (R=0.80), SS (R=-0.693), LL (R=-0.682), PI-LL (R=0.7237), SVA (R=0.561) and TPA (R=0.696). There was a weak correlation with TK and T1SPi. AV was decreased by 1degree for each of the following iatrogenic changes in spino-pelvic parameters (p<0001): 1.1degree PT, -1degree SS, 3.2degree LL, 1.67degree TPA and -11mm SVA. Thirty (73%) of acetabular components had a preoperative AVoutside the Lewinneck "safe zones." Twenty-eight of these 30 were excessively anteverted as a result of increased preoperative pelvic tilt. Postoperatively, 49% of patients still had an AV outside the safe zone, with 65% of these having residual pelvic tilt>20degree. Correction of SSD moved one acetabulum (2.4%) from a safe to unsafe AV. CONCLUSIONS: Correction of SSD results in reduction in AV, with potential implications for THA stability. SSD correction, when indicated, should be performed prior to THA to enable accurate acetabular positioning and minimize potential for dislocation. This study provides an algorithm for the sequence of THA and SSD correction in the patient with concominant pathologies

The triple-taper cemented femoral stem was developed to promote proximal femoral and calcar loading to minimize periprosthetic bone loss and aseptic loosening. Periprosthetic changes in bone mineral density in Gruen zones 1 to 7 were analyzed in 103 patients over a 2-year period using dual x-ray absorptiometry. There was a statistically significant decrease in bone mineral density in all Gruen zones, but was most marked in zones 1 and 7. Periprosthetic bone density was reduced significantly in the first 3 to 9 months, after which recovery of bone density occurred. Greater calcar bone loss was seen in women, patients with a low preoperative bone density, and patients with poor postoperative mobility. Age at surgery did not effect calcar bone loss.

BACKGROUND: Image-guided stereotaxy is a recent advancement in imaging technology, allowing computer guidance to aid surgical planning and accuracy. Despite the use of multiple techniques for patient registration in several surgical specialities, only fiducial marker registration has been described for use in soft tissue reconstructive surgery. The current study comprises an evaluation of the current techniques available for this purpose. METHODS: A cohort of nine consecutive patients planned for elective free flaps were recruited, with the first five patients (four for the abdominal wall and one anterolateral thigh donor site) undergoing fiducial marker registration with a variable number of fiducial markers in order to determine the optimal number of fiducial markers to be used. Four subsequent patients undergoing perforator flap surgery underwent registration using three available registration modalities: fiducial marker registration, surface matching pointer/landmark and surface matching laser registration. RESULTS: For the abdominal wall, registration was not able to be achieved with five fiducial markers, and was successfully achieved in all cases with either six or seven fiducial markers. For the anterolateral thigh, registration was achieved with either nine or ten markers. The four patients who also underwent surface-landmark registration and 'Z-touch' laser surface matching registration all failed the registration process. CONCLUSION: Stereotactic navigation is a useful adjunct to the preoperative imaging of perforator flaps. Fiducial marker registration was able to be achieved in all cases, can be successfully achieved with a low and predictable number of fiducial markers, is highly accurate, and was the only reliable registration process in our experience.

BACKGROUND: The sartorius muscle is a superficial muscle of the thigh that possesses highly suitable qualities for many uses in local transposition and free muscle transfer. However, a paucity of description of the neurovascular anatomy of the sartorius has contributed to its infrequent use in these roles. METHODS: Both human and canine studies were undertaken to delineate the neurovascular anatomy of the sartorius and to determine the role for surgical delay clinically. Fifty-five human cadaveric sartorius muscles and 30 canine cadaveric sartorius muscles underwent angiographic and dissection studies, and the location and course of the vessels and nerves supplying sartorius are described. A subsequent study was undertaken in two live canines in which the vascular supply to the sartorius was evaluated before and after surgical delay. RESULTS: The sartorius is supplied by an average of six or seven vascular pedicles, the size, location, and course of which are described. The nerve supply to the sartorius enters at its proximal end and uniformly arises from a branch of the femoral nerve. Variations in branching patterns and course of nerves and vessels are described. Living canine studies demonstrated the dilatation of intramuscular vessels following surgical delay, with the contrast injection of a single remaining vascular pedicle shown to vascularize the entire length of the sartorius muscle. CONCLUSIONS: The sartorius is highly suitable for local transposition and free muscle transfer for facial reanimation. The neurovascular anatomy is reliable, and the use of surgical delay can augment its vascular supply and increase the arc of rotation for local transposition.

AIM: To quantify and qualify the types of upper limb injuries admitted to hospital as a direct result of illicit intravenous drug use (IVDU). METHOD: A retrospective case series identified all inpatient admissions for upper limb injuries as a direct result of IVDU over a two-year period. The type of injury, procedures, complications, co-morbidities, relevant investigations and other notable events during admission and follow-up were identified. RESULTS: Thirty-six people were admitted with upper limb injuries. Infective presentations (abscess, cellulitis, osteomyelitis, and septic arthritis) were most common. Other injuries were due to accidental intra-arterial injection, soft-tissue necrosis and compartment syndrome. Microbiological analysis from abscesses showed a high frequency of multiple organisms, and most commonly identified Streptococci, Staphylococcus aureus, and anaerobes. These patients had high rates of hepatitis C, malnutrition, psychiatric and behavioural co-morbidities; 77% were lost to follow-up. CONCLUSION: The most common injuries from IVDU are infections, and ischaemia. High rates of concurrent medical and psychosocial co-morbidities add further challenges to effective patient care.