Of the seven studies that included pre and post-operative outcomes three documented increases in hip flexion active range of motion (AROM), one by a mean of 18.9 degrees, one noted a significant improvement, and another showed a mean hip flexion of 120.36 degrees [12,29,15]
. Six assessed the Harris Hip Score (HHS) and noted the following: an increase of 56, means of 96.4 and 84.8, poorer outcomes with lesser Charnley grades, one simply noted improvement, and two noted significant improvement [12,21,23–25,28,29]
. The four studies which noted the Oxford Hip Score (OHS) found means of 16.1 and 16.4, a mean 26.3 improvement, a mean of 21.4, and poorer outcomes with lower Charnley grades [12,24,25]
. One study reported the median modified OHS as 4.2% using the Pynsent method 
. The five that documented the University of California Los Angeles Activity Score (UCLA AS) noted means of 6.6 and 6.7, a 3.61 improvement, a mean of 8.4, statistical improvement, and a median of 7.0 [14,16–18,24]
One study included a pre and post-operative questionnaire and had participants’ complete information on sports participation before and after BHR. 65% were active in sports preoperatively, and this increased to 92% postoperatively. 92% reported that their sporting function had improved. There was a significant difference in the intensity and frequency of sports participation 
Of the six studies which detailed only post-operative outcomes, those that used the HHS reported means of 95.3, 97.24 and 84.8 [15,25,26]
. One author reported that the HHS had him conclude that BHR was effective for a younger, active population. The scores were not reported 
. On those that used the UCLA AS provided means of 8.4 
and 6.7 
Studies reporting the OHS listed means of 15.9 
and 16.4 
One study reported satisfaction means of 2.53 out of a 0 (poor) to 3 (excellent) scale 
. Finally, where AROM hip flexion was considered, the mean was 100 degrees 
The three studies which contained only post operative questionnaires included reports of adverse events, sports participation, and employment status [19,20,27]
. Adverse events were less than one percent. Sports participation was reported to have declined in high and intermediate impact activities and increased in low impact activities. One third of the subjects reported they had to give up sports that they intended on continuing. Employment surveys showed 90% of patients’ employment was not affected.
The research identified using outcomes to report on BHR falls into the Level of Evidence: 4 of the Sackett scale. Level 4 is defined as a “Case series and poor quality cohort and case-control studies” 
. This limitation in research design does not allow for a complete appreciation of the outcomes of BHR, either on its own or in comparison with THA, arthroscopic procedures, other hip resurfacing systems, or absence of surgical intervention.
The quality assessment scale as defined by AACPDM in the included research had a mean of 3.25 on the 7 point scale. Only three of the studies presented clear inclusion and exclusion criteria. Six of the studies clearly noted the surgical approach utilized, while four contained comments concerning the post-operative care and/or rehabilitation. While some of the outcome tools used, such as the HHS, OHS, and UCLA AS have been shown to be valid, their reliability when applied to BHR has not yet been established. None of the studies utilized any type of blinding when assessing the patients. Use of statistical evaluation and power analysis varied in the research. Finally, the dropout/loss rate was typically below the established 20% and reported failure rates were acceptable.