A police force has been urged to fit safety guards to all its cell doors after a man had part of three fingers chopped off.
Jamie Clark, 29, lost his fingers in the cell door after being wrongly accused of assaulting a police officer.
The police watchdog ruled there was insufficient evidence to bring a misconduct case against any officers.
But the Independent Police Complaints Commission did call on the force to consider cell door "finger guards".
Mr Clark, of Burry Port, Carmarthenshire, was initially arrested after a row with his girlfriend in June 2016 but was accused of attempting to assault PC Christopher Burton at Llanelli police station following his arrest.
The father-of-one won a legal battle to seize CCTV footage of the incident.
He gave the video footage to the IPCC as part of a formal complaint over his treatment.
An IPCC spokesman said: "The force accepted recommendations to remind custody officers that significant events and decisions should be recorded in detail and to ensure custody staff training looks at minimising any risk of injury to detainees during the closure of cell doors.
"Dyfed-Powys Police also planned to assess the possibility of installing finger guards in custody suites."
Mr Clark, a self-employed painter, claimed he was pepper sprayed, stripped naked and forced into a cell by half a dozen officers.
"I went to get out but that's when I felt this huge pain and felt my flesh being torn away when the door was shut," he said last year.
"I was screaming in agony. I was begging the officers to open the door but no-one helped me."
A Dyfed-Powys Police spokesman said it accepted the conclusion from the IPCC.
The force has "complied with recommendations from the IPCC, including adding a new element around finger safety to training and reviewing the possibility of finger guards", he added.