Introduction. Our classic outcome scores increasingly fail to distinguish interventions or to reflect rising patient demands. Scores are subjective, have a low ceiling and score pain rather than function. Objective functional assessment tools for routine clinical use are required. This study validates inertial sensor motion analysis (IMA) by differentiating patients with knee versus hip osteoarthritis in a block-step test. Methods. Step up and down from a block (h=20cm, 3 repetitions) loading the affected (A) and unaffected (UA) leg was measured in n=59 subjects using a small inertial sensor (3D gyro and accelerometer, m=39g) attached onto the sacrum. Patients indicated for either primary unilateral THA (n=20; m/f=4/6, age=69.4yrs ±9.8) or TKA (n=16;m/f=7/9;age=67.8yrs ±8.2) were compared to healthy controls (n=23;m/f=13/10;age=61.7yrs ±6.2) and between each other to validate the test's capacity for diagnostics and as an outcome measure. The motion parameters derived (semi-) automatically in Matlab for both legs were: front-back (FB-) sway and left-right (LR-) sway (up and down); peak-to-peak accelerations (Acc) during step down. In addition the asymmetry between both legs (ASS) was calculated for each parameter. Group differences were tested (t-test) and the diagnostic value determined by the area under the curve (AUC) of the ROC-curve. Results. During step-up FB-sway was higher for THA (20.4°±4.9) and TKA (21.7°±5.9) patients than for healthy controls (15.5°±3.4, p<0.001). Also asymmetry was higher (THA=20%, TKA=21%, H=11%, p<0.001). Results were similar during step down except for the affected leg of THA patients where FB-sway (THA=16.2°±3.0) was similar to controls but sign. different to TKA patients (22.2±4.4) producing a high diagnostic power (AUC=0.88) to differentiate THA and TKA. LR-sway was also indicative for THA patients being the only subjects showing high asymmetry between the legs (A=14.3°±3.7 vs UA=11.9°±3.1, p<0.001). Acceleration during step-down asymmetric in patients, especially in THA (H<TKA<THA;p<0.05; AUC=0.87). Discussion. The IMA-block-step test could detect pathology specific compensation mechanism: During step-up patients use more FB-sway (+29%) to generate momentum for compensating muscle weakness and decrease joint loading. During step-down, only THA patients showed less FB-sway with their affected leg avoiding the painful hip flexion. Also in THA the LR-sway was higher in the affected than unaffected side due to the typical abductor weakness and resulting Trendelenburg sign. The IMA-block-step test could objectify compensation mechanisms used in OA and showed the power to differentiate between H, TKA and THA. It is low cost and fast to perform (<5min) by non-specialist personnel and thus could be used in clinical routine to supplement questionnaire based outcome scores

There remains uncertainty about the most effective surgical approach in the treatment of complex fractures of the acetabulum. We have reviewed the experience of a single surgeon using the extended iliofemoral approach, as described by Letournel.

A review of the database of such fractures identified 106 patients operated on using this approach with a minimum follow-up of two years. All data were collected prospectively. The fractures involved both columns in 64 (60%). Operation was undertaken in less than 21 days after injury in 71 patients (67%) and in 35 (33%) the procedure was carried out later than this. The reduction of the fracture was measured on plain radiographs taken after operation and defined as anatomical (0 to 1 mm of displacement); imperfect (2 to 3 mm) or poor (> 3 mm). The functional outcome was measured by the modified Merle d’Aubigné and Postel score. The mean follow-up was for 6.3 years (2 to 17).

All patients achieved union of the fractures. The reduction was graded as anatomical in 76 (72%) of the patients, imperfect in 23 (22%), and poor in six (6%). The mean Merle d’Aubigné and Postel score was 15 (5 to 18) with 68 patients (64%) showing good or excellent and 38 (36%) fair or poor results. Function correlated significantly with the accuracy of the reduction (p < 0.009). Significant heterotopic ossification developed in 32 patients (30%) and was associated with a worse mean Merle d’Aubigné and Postel score of 13.7.

The extended iliofemoral approach can be performed safely in selected complex acetabular fractures with an acceptable clinical outcome and rate of complications. Effective prophylaxis against heterotopic ossification should be strongly considered.