Insufficient lateral stem contact is an influencing factor for significant subsidence in cementless short stem total hip arthroplasty

BACKGROUND

Subsidence is one of the concerning early complications in cementless femoral stem. Few publications have studied the influencing factors for subsidence in short cementless stems, due to their metaphyseal anchoring without diaphyseal invasion, they might demonstrate different subsidence patterns than with the conventional stems.

AIM

To analyze the factors associated with significant subsidence in short stems, including any radiographic parameters.

METHODS

The digitized radiographs of 274 consecutive short stem total hip arthroplasties were retrospectively reviewed. Subsidence, neck-filling ratio (NFR), seating height and lateral stem contact were evaluated after a minimum of two years follow-up. A threshold of subsidence > 3 mm was considered a clinically significant migration.

RESULTS

For the entire cohort, subsidence occurred in 75 cases (27.4%) with the mean stem subsidence of 0.5 mm. (0-12.7, 1.68). Twelve hips (4.4%) had significant subsidence (> 3 mm). The univariate regression analysis demonstrated that age, diagnosis, BMI, Dorr’s type B, NFR, and seating height had no significant influence on significant subsidence, whereas insufficient lateral stem contact (≥ 1 mm) did have a statistically significant influence [Odds ratio (OR) = 5.02; 95%CI: 1.3-18.9; P = 0.017]. The multivariate regression analysis also demonstrated that insufficient lateral stem contact was a statistically significant influencing factor (OR = 5.5; 95%CI: 1.4-21.4; P = 0.014). There was no femoral stem revision for aseptic loosening in our cohort.

CONCLUSION

This study demonstrated that insufficient lateral stem contact was a statistically significant influencing factor on significant subsidence. Therefore, it is a particularly important step to create proper lateral cortical contact when performing the short stem total hip arthroplasty.

Mid-term results of short stem total hip arthroplasty in patients with osteonecrosis of the femoral head

PURPOSE

To evaluate the clinical and radiographic mid-term results of short-stem total hip arthroplasty (THA) in patients with osteonecrosis of the femoral head (ONFH).

METHODS

We reviewed 83 cases that underwent Metha stem between November 2010 and November 2012. The appearance of bone trabeculae development and radiolucent line were reviewed and HHS was recorded at 6 months postoperatively then yearly to evaluate the clinical results.

RESULTS

The mean age of patients was 43.8 years with the mean follow-up 69.3 (60-84) months. Harris Hip Score improved significantly from 44.7 preoperatively to 99.6 at the last follow-up (p < 0.0001). There were 4 cases (4.8%) of intraoperative femoral fractures. There was 1 case (1.2%) of distal stem perforation that had stable bone ingrowth and there was 1 case (1.2%) of 5-mm subsidence, which was then stable at 3 months postoperatively. Bone trabecular development was detected at zone 1 (65.1%), 2 (69.9%), 3 (14.4%), 4 (1.2%), 6 (97.6%) and 7 (81.9%). There was 1 case (1.2%) where radiolucent lines were observed in zones 1 and 7. There was 1 femoral stem revision from periprosthetic fracture 4 years after index surgery and 1 cup revision from aseptic loosening. Kaplan-Meier survivorship with the end point of stem revision for any reason was 98.8% and for aseptic loosening it was 100% at 7 years.

CONCLUSIONS

The mid-term clinical and radiographic results of the Metha stem in patients with ONFH were promising. Its design enables preservation of the bone stock and the bone trabeculae appear to confirm the assumption of proximal force transmission.

Deviation of cup alignment from target angle during press-fit insertion

BACKGROUND

Several factors lead to cup malalignment including preoperative pelvic tilt, inaccurate pelvic position on the operating table, pelvic movement during the operation and alignment change after screw fixation of the cup. There are few studies about the deviation of cup alignment from target angle during press-fit insertion, which may be the other cause of cup malalignment. The purpose of this study was to evaluate the deviation of cup alignment from target angle during press-fit insertion by using imageless navigation and to define any influential factors, including gender, age and side of operation.

METHODS

Between February 2016 and March 2017, patients undergoing total hip arthroplasty (THA) with imageless navigation were included in the present single-center study. Cup inclination angle was set at 40 degrees in all cases but the anteversion angle varied depending on the stem anteversion in each case using a combined anteversion technique. The final cup was aligned at target angles in both inclination and anteversion, the tracker was detached from the insertion handle and the surgeon inserted the cup until it was seated completely. The tracker was attached again to display both inclination and anteversion angles and these angles were recorded. Deviated Inclination Angles (DIA) and Deviated Anteversion Angles (DAA) in each case were calculated.

RESULTS

There were 124 cases in the present study. The mean age of the patients was 60.2 years (25-93). There were equal numbers of right-sided and left-sided operations, 62 cases each. There were 114 cases (91.9%) with DIA. The mean DIA was 2.65^° (0^°-8^°, SD 1.66). The DIA decreased in 107 cases (86.3%) with 12 cases (9.7%) showing a decrease of 5^° or more. The DIA increased in 7 cases (5.6%) with 2 cases (1.6%) showing an increase of 5^° or more. There were 103 cases (83.1%) with DAA. The mean DAA was 2.3^° (0^°-14^°, SD 2.3). The DAA increased in 78 cases (62.9%) with 11 cases (8.3%) increasing by 5^° or more. The DAA decreased in 25 cases (20.2%) with 4 cases (3.2%) decreasing by 5^° or more. The DIA was significantly higher in males than in females (p = .012). There was significant correlation between DAA and patient's age (p = .037). There was no significant difference between DIA or DAA and side of operation.

CONCLUSION

Changes in cup orientation were observed in most cases during cup insertion with hammer blows detected by imageless navigation. Deviation of cup alignment from target angle during press-fit insertion was a possible cause of cup malalignment, male gender and patient's age were influential factors.

Precision of Limb Length Measurement in Imageless Navigation THA with Modified Registration Technique in Semilateral Decubitus Position

BACKGROUND

Limb length discrepancy (LLD) following total hip arthroplasty (THA) can be a significant problem and leading to patient dissatisfaction. Several researchers have reported that imageless navigation is a reliable technique and results in more precise cup placement compared to conventional freehand techniques, however, few studies have been reported about the accuracy of the femoral stem placement.

OBJECTIVE

(1) To evaluate the precision of an imageless navigation system in measuring the limb length change and (2) to evaluate LLD following imageless navigation THA with modified registration technique in semilateral decubitus position.

MATERIAL AND METHOD

The authors reviewed 66 cases receiving cementless THA with imageless navigation from September 2013 to December 2014. The radiographic limb length change measured from pre-operative and post-operative digital x-ray was compared with the intraoperative calculation by the navigation system. Postoperative LLD in unilateral cases and second operation of staged bilateral cases were also recorded

RESULTS

The mean radiographic limb length change measured on digital x-ray was 17.4 mm (5 to 29.3, SD 5.7). The mean limb length change calculated by navigation system was 16.8 mm (3 to 28,SD 5.9). The mean paired difference was 2.27 mm (-6 to 8, SD 0.9). This difference was significant (p = 0.01). There was significant correlation between LL change measured on digital x-ray and which were calculated by navigation system (r = 0.95, p<0.001). The navigation system had an accuracy of within 1 mm of the radiographic measurement in 7.6% of cases, within 2 mm in 39.4% of cases and within 5 mm in 93.9% of cases. The mean postoperative LLD was 2 mm (0 to 7, SD 1.9), 92% were within 5 mm.

CONCLUSION

The present study showed that the imageless navigation THA with modified registration technique in semilateral decubitus position offered a precise limb length measurement and the results encouraged us for clinical use to minimize LLD in THA.

The Short Stem THA Provides Promising Results in Patients with Osteonecrosis of the Femoral Head

BACKGROUND

The short stem prosthesis showed good results in patients with primary osteoarthritis. However there were afew studies about the short stem total hip arthroplasty (THA) in patients with osteonecrosis of thefemoral head (ONFH).

OBJECTIVE

To evaluate the clinical and radiographic results of the short stem THA in patients with ONFH. The authors hypothesized that the short stem THA would be a promising procedure for patients with ONFH.

MATERIAL AND METHOD

The authors reviewed 120 osteonecrotic hips in 93 patients who underwent THA with Metha® short stem between November 2010 and February 2013. The appearance of bone trabeculae development and radiolucent line was reviewed using Gruen's classification. The Harris hip score (HHS) was recorded at 6, 12, 24, and 36 monthspostoperative for evaluating the clinical results.

RESULTS

The mean age of patients was 44.4 years (18-68) with the mean BMI of 22.7 (15.1-32.5, SD 3.5). The average follow-up period was 29.2 months (20-47). The mean HHS was significantly improved from 43.9 (22.7-74, SD 7.7) preoperatively to 97.7 (85.9-100, SD 2.7) at 6-month postoperatively (p < 0.01). The radiographic change around the stems showed bone trabeculae development at zone 1 (77 cases, 64.2%), 2 (27 cases, 22.5%), 3 (106 cases, 88.3%), 6 (120 cases, 100%), and 7 (115 cases, 95.8%). There was one case (0.8%) of 5 mm subsidence and the radiolucent line was observed in zone 1. There were six cases (5%) of intraoperativefemoralfractures and were treated with cerclage wires with nofurther subsidence observed There was one case (0.8%) of distal stem perforation that had stable bone ingrowth. No revision was required.

CONCLUSION

The clinical and radiographic results of the short stem THA in patients with ONFH are generally satisfactory. Its design enables preservation of the bone stock and the bone trabeculae appear to confirm the assumption of proximal force transmission. The authors believe that the short stem THA is a promising procedure for patients with ONFH.

Initial clinical and radiographic results with the short stem THA

BACKGROUND

The patient who suitable for short stem THA must has good neck quality for initial stable fixation. In Thailand, the majority of patients are end stage osteonecrosis and have relatively narrow neck diameter so it's may be increased risk of intraoperative femoral fractures and leading to stem failure.

OBJECTIVE

Evaluate the initial clinical and radiographic results of short stem THA over a maximum follow-up period of about 24 months, paying special attention to early problem.

MATERIAL AND METHOD

The case series of 50 patients receiving short stem THA during March 2010 to September 2011. There were 15 cases of Mayo stem and 35 cases of Metha stem. The appearance of bone trabeculae development and radiolucent line at 1 year postoperative was reviewed using Gruen's classification. The Harris hip score was recorded at 6 months, 12 months and 24 months postoperative for evaluated the clinical results.

RESULTS

In Mayo stem group, the mean age of patient was 44.2 years (range, 19-58) with the mean BMI of 20.9 (range, 16.9-28.1). There were 2 cases of intraoperative fractures and were treated with cerclage wires, 1 case had 3 mm subsidence with radiolucent line in zone 1, 2. Bone trabeculae was developed at zone 2 (60%), 6 (86.7%), 7 (53.3%) and radiolucent line was observed at zone 1 (6.7%) and zone 2 (6.7%). In Metha stem group, the mean age of patient was 43.9 years (range, 24-59) with the mean BMI of 22.2 (range, 16.5-32.3). There was 1 case of intraoperative fracture and was treated with cerclage wire, no further subsidence was observed. Bone trabeculae was developed at zone 1 (15.4%), 3 (79.9%), 6 (100%), 7 (92.3%) and no radiolucent line was observed. The mean Harris hip score was significantly improved from 44.9 (range, 22.7-59.7) preoperatively to 95.9 (range, 87-100) at 6 months (p < 0.01) in both stem design.

CONCLUSION

The clinical results of short stem THA are generally satisfactory. The short-term results are promising and the learning curve acceptable. Its design enable preservation of the bone stock and the bone trabeculae appears to confirm the assumption of proximal force transmission. It is a promising option for young and active patients.