Background

Four mechanical alignment force targets are used to predict early patient-reported outcomes and/or to indicate a balanced TKA. For surgeons who use kinematic alignment, there are no reported force targets. To date the usefulness of these mechanical alignment force targets with kinematic alignment has not been reported nor has a specific force target for kinematic alignment been identified.

Questions/purposes

(1) Does hitting one of four mechanical alignment force targets proposed by Gustke, Jacobs, Meere, and Menghini determine whether a patient with a kinematically aligned TKA had better patient-reported Oxford Knee and WOMAC scores at 6 months? (2) Can a new force target be identified for kinematic alignment that determines whether the patient had a good/excellent Oxford Knee Score of ≥ 34 points (48 best, 0 worst)?

Methods

Between July 2017 and November 2017, we performed 148 consecutive primary TKAs of which all were treated with kinematic alignment using 10 caliper measurements and verification checks. A total of 68 of the 148 (46%) TKAs performed during the study period had intraoperative measurements of medial and lateral tibial compartment forces during passive motion with an instrumented tibial insert and were evaluated in this retrospective study. Because the surgeon and surgical team were blinded from the display showing the compartment forces, there was no attempt to hit a mechanical alignment force target when balancing the knee. The Oxford Knee Score and WOMAC score measured patient-reported outcomes at 6 months postoperatively. For each mechanical alignment force target, a Wilcoxon rank-sum test determined whether patients who hit the target had better outcome scores than those who missed. An area under the curve (AUC) analysis tried to identify a new force target for kinematic alignment at full extension and 10°, 30°, 45°, 60°, 75°, and 90° of flexion that predicted whether patients had a good/excellent Oxford Knee Score, defined as a score of ≥ 34 points.

Results

Patients who hit or missed each of the four mechanical alignment force targets did not have higher or lower Oxford Knee Scores and WOMAC scores at 6 months. Using the Gustke force target as a representative example, the Oxford Knee Score of 41 ± 6 and WOMAC score of 13 ± 11 for the 31 patients who hit the target were not different from the Oxford Knee Score of 39 ± 8 (p = 0.436) and WOMAC score of 17 ± 17 (p = 0.463) for the 37 patients who missed the target. The low observed AUCs (from 0.56 to 0.58) at each of these flexion angles failed to identify a new kinematic alignment force target associated with a good/excellent (≥ 34) Oxford Knee Score.

Conclusions

Tibial compartment forces comparable to those reported for the native knee and insufficient sensitivity of the Oxford Knee and WOMAC scores might explain why mechanical alignment force targets were not useful and a force target was not identified for kinematic alignment. Intraoperative sensors may allow surgeons to measure forces very precisely in the operating room, but that level of precision is not called for to achieve a good/excellent result after calipered kinematically aligned TKA, and so its use may simply add expense and time but does not improve the results from the patient's viewpoint.

Level of evidence

Level III, therapeutic study.

Purpose

Determine whether patient pain and function are similar following hip abductor repair in patients without and with total hip arthroplasty (THA).

Methods

Patients who underwent hip abductor repair were categorized as to whether they had a THA or not. Pre- and postoperative pain and Harris Hip Score (HHS) were recorded and compared between groups.

Results

There were no differences in improvement in pain level, improvement in HHS, satisfaction with surgery.

Conclusions

Hip abductor repair leads to similar pain, function, and satisfaction in patients without and with THA.

Background

Although proximal humerus strength/quality can be assessed using cortical thickness measurements (eg, cortical index), there is no agreement where to make them. Tingart and coworkers used measurements where the proximal endosteum becomes parallel, while Mather and coworkers used measurements where the periosteum becomes parallel. The new circle-fit method (CFM) makes 2 metaphyseal (M1-M2) and 6 diaphyseal (D1-D6) measurements referenced from humeral head diameter (HHD). However, it is unknown whether these locations correlate to humeral length (HL). Accordingly, we asked: (1) Does HHD, Tingart distance, and Mather distance correlate with HL? (2) What is the location of HHD, Tingart distance, and Mather distance as a percentage of HL? and (3) Which CFM D1-D6 locations correlate with Tingart and Mather distances?

Materials and methods

Measurements made on cortical thickness (CT) scout views of 19 humeri (ages: 16-73 years) included HHD, distances from the superior aspect of the humerus to proximal Tingart and Mather locations, and HL.

Results

Intraclass correlation was excellent for CFM-HHD, poor for Tingart, and moderate for Mather. The CFM-HHD had a stronger correlation to HL than Tingart and Mather. Mean HHD was 15.5% (0.9%) of HL while Tingart was 27.0% (4.1%) and Mather was 23.2% (3.8%). Tingart distance corresponded to D2/D3 CFM locations while the Mather distance was similar to D1/D2.

Discussion

The CFM reliably correlates with HL and provides a stronger correlation and less variance between specimens than the Tingart or Mather Methods.

Conclusions

Because the CFM produces reliable percent of HL locations, it should be used to define locations for obtaining biomechanically relevant CT measurements such as cortical index. Stronger correlations of these CFM-based measurements with proximal humerus strength will be important for developing advanced algorithms for fracture treatment.

Purpose

Intertrochanteric (IT) hip fractures can be treated with sliding hip screws (SHS) or cephalomedullary nails (CMN) based on the stability of the fracture. This stability is affected by the initial impaction of the fracture which can be difficult to assess. The aim of this paper is to develop specific pre-operative computed tomography (CT) measurements of IT fractures which are predictive of post-operative shortening.

Methods

A retrospective review was performed of 141 patients with AO/OTA 31A1 or 31A2 fracture patterns, who had pre-operative radiographs and CT scans, and who were treated with a SHS or a CMN. Pre-operative and post-operative imaging of IT fractures were analyzed for those fractures that shortened ≥15 mm post-fixation.

Results

11 fractures shortened ≥15 mm with CMN being protective of shortening (6/36 SHS versus 5/105 CMN, p = 0.0268). A novel measurement made on the pre-operative CT scan called the cortical thin point (CTP) detected differences between patients with <15 mm and ≥15 mm of post-operative shortening for the SHS group (p = 0.0375). CTP was found to be a reliable predictor for post-operative shortening of ≥15 mm when a cutoff threshold of 9 mm was used in the SHS group (p = 0.0161).

Conclusions

Measuring the CTP is predictive of post-operative shortening after fixation of an IT fracture with a SHS. CMN fixation may be protective of shortening. Patients with a CTP of ≤9 mm are at risk for fracture site shortening of more than 15 mm when treated with a SHS.

Our previous studies used tibial compression overload to induce anterior cruciate ligament (ACL) rupture in mice, while others have applied similar or greater compressive magnitudes without injury. The causes of these differences in injury threshold are not known. In this study, we compared knee injury thresholds using a "prone configuration" and a "supine configuration" that differed with respect to hip, knee, and ankle flexion, and utilized different fixtures to stabilize the knee. Right limbs of female and male C57BL/6 mice were loaded using the prone configuration, while left limbs were loaded using the supine configuration. Mice underwent progressive loading from 2 to 20 N, or cyclic loading at 9 N or 14 N (n = 9-11/sex/loading method). Progressive loading with the prone configuration resulted in ACL rupture at an average of 10.2 ± 0.9 N for females and 11.4 ± 0.7 N for males. In contrast, progressive loading with the supine configuration resulted in ACL rupture in only 36% of female mice and 50% of male mice. Cyclic loading with the prone configuration resulted in ACL rupture after 15 ± 8 cycles for females and 24 ± 27 cycles for males at 9 N, and always during the first cycle for both sexes at 14 N. In contrast, cyclic loading with the supine configuration was able to complete 1,200 cycles at 9 N without injury for both sexes, and an average of 45 ± 41 cycles for females and 49 ± 25 cycles for males at 14 N before ACL rupture. These results show that tibial compression configurations can strongly affect knee injury thresholds during loading.

To compare the efficacy of plain x-ray images and computed tomography (CT) to assess the morphology of the lateral wall (LW) component of intertrochanteric (IT) femur fractures and determine predictors of early fixation failure.

Design

Retrospective cohort study.

Setting

Level-one trauma center.

Patients/participants

One hundred forty-two adult patients with IT fractures treated with either a sliding hip screw (SHS) or a cephalomedullary nail (CMN) who had both pre-op plain x-ray images and CT scans with at least 6 weeks of follow-up were reviewed.

Intervention

Preoperative CT scan and plain radiographs of the affected hip.

Main outcome measurements

Lateral wall assessment based on plain x-rays versus CT imaging in relation to implant failure.

Results

One hundred forty-two patients met inclusion criteria, 105 patients treated with a CMN, and 37 with a SHS. There was a poor correlation between the assessment of the LW on plain x-ray images and CT scans. Failures in the SHS group were significantly associated with all CT measurements (P < .05) but not with plain film LW assessment (P = .66). Fifteen patients had an early implant failure (6 CMN, 9 SHS). There were no statistically significant associations between any radiographic measurement (plain images and CT) and CMN failures.

Conclusions

Plain film images are not accurate for assessing lateral wall morphology/integrity and are not predictive of SHS implant failures. Our novel CT measurements were effective at detecting lateral wall patterns at risk for treatment failure with SHS implants.Level of Evidence: Level III.